The present invention relates to an improvement in fluidized-bed calciners for the processing of liquids containing dissolved or entrained solids to form dry solid particles. It has application in the dehydration and denitration of radioactive waste material, both in slurry and in solution. The development also can be used in other solidification, dehydration and calcination processes such as in the processing of fertilizers and industrial chemicals.
Previous fluidized-bed calciners employing in-bed combustion of fuel have discharged mixtures of fuel with oxygen or air directly into the fluidized bed for combustion. The immediate dissemination of the fuel mixture throughout the fluidized bed can produce poor combustion efficiency. Also, the combustion gases discharged from the burner at high velocities and temperatures can cause attrition of bed particles with the production of fines. In radioactive waste processes where no contaminants can be released, the fine particles are particularly undesirable. The hot combustion gases can melt or soften bed particles, resulting in the formation of agglomerates or clinkers, particularly around the burner. The burner nozzles also can sustain severe erosion by exposure to the fluidized bed at the elevated temperatures.
The inventors, being aware of these problems in prior art in-bed combustion systems, have provided as their invention an improved fuel burner assembly for use within a fluidized-bed calciner.
It is an object of their invention to produce such an improved fuel burner assembly that will minimize attrition of fluidized-bed particles and production of fines.
It is a further object to increase combustion efficiency of fuel.
It is also an object to protect the fuel nozzle within the burner from erosion and clinker formation on and about its surfaces.